CLINICAL
DIABETES These pages are best viewed with Netscape version 3.0 or higher or Internet Explorer version 3.0 or higher. When viewed with other browsers, some characters or attributes may not be rendered correctly. E d i t o r i a l When Does Diabetes Begin, and How Do We Know It? Alan J. Garber, MD, PhD, Editor Unlike type 1 diabetes, which has a seemingly abrupt clinical onset heralded by the appearance of well-defined clinical symptomatology, type 2 diabetes evolves slowly over decades and often presents with no antecedent or current symptomatology. Commonly, type 2 diabetes is diagnosed as the result of a routine evaluation or screening procedure. Unfortunately, it is also often diagnosed at the time of presentation with an end-stage complication of diabetes, such as an acute coronary event or vision-threatening retinopathy. Fasting hyperglycemia is not distributed in a bimodal fashion, there being no clearly normal population and a second, discreet diabetic population. Instead, the distribution of fasting blood glucose levels suggests a continuum, with the upper limits of the nondiabetic population merging into the diabetic population. One may, therefore, identify patients with diabetes more reliably on the basis of risk of developing classic diabetic complications, such as retinopathy, nephropathy, and neuropathy, and because of increased cardiovascular risk. Formerly, patients were diagnosed at a fasting blood glucose level >140 mg/dl or a 2-hour post-challenge blood glucose level of >200 mg/dl because of the definable increase in the risk of the microvascular complications of diabetes. However, these diagnostic criteria are inadequate to prevent a significant minority of newly diagnosed patients from already having pre-existing diabetic complications. Thus, more than half of newly diagnosed patients with type 2 diabetes have been found to have clinically significant coronary disease, and more than 20% have evident retinopathy. Additionally, a significant proportion of patients with fasting serum glucose levels <139 mg/dl have 2-hour post-glucose values of >200 mg/dl when tested with a 75-gram glucose tolerance test. For these reasons, the American Diabetes Association appointed an expert panel to carefully review the epidemiological data concerning the diagnosis of diabetes. Their conclusion, based on a careful analysis described in the July 1997 issue of Diabetes Care and reprinted in this issue on page 158, is to lower the diagnostic threshold for diabetes to 126 mg/dl fasting. Fully half of all patients with otherwise normal fasting glucose levels (<139 mg/dl) yet failing a glucose tolerance test (>200 mg/dl at 2 hours) will be diagnosed as having diabetes based solely on the downward revision of the fasting glucose criterion for diabetes diagnosis. Some physicians have objected to this revision of the diagnostic threshold for diabetes based primarily on its implications for additional therapeutic efforts toward glycemic control. Many primary care practitioners do indeed have difficulty reducing fasting blood glucose levels to 140 mg/dl or lower in their patients with diabetes, and they believe that this difficulty will be compounded if the diagnostic threshold is reduced to 126 mg/dl. Nothing could be less relevant to the issue at hand. Regardless of the difficulty in achieving normoglycemia, a diagnosis of diabetes depends upon a reproducible demonstration that patients with this diagnosis will ultimately develop the chronic complications of the disease. Furthermore, treatment goals for patients with diabetes are as yet unchanged. It may be that such goals will be lowered in the future. On the other hand, one should not be content with fasting blood glucose levels as high as 139 mg/dl or HbA1c levels up as high as 7.9%. The current goals of diabetes therapy are significantly lower. Mistaking the upper limit of acceptable control where action is necessary for the true goal of therapy is a common misperception that requires correction. Goals for diabetes therapy, as stated in numerous American Diabetes Association position statements, are clear and well-defined: fasting serum or plasma glucose levels of <120 mg/dl and an HbA1c level of <7.0%. While these numbers are difficult to obtain, we should not devalue our goals because of that difficulty. And, as we see virtually every day, new technologies and treatments that improve our ability to improve glycemic control are rapidly becoming available. Copyright © 1997 American Diabetes Association Last updated: 9//97 For Technical Issues
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